CA2180558A1 - Process for preparation of reduced metal titanium complexes - Google Patents

Abstract

A process for preparing titanium or zirconium hydrocarbyloxide complexes in a reduced oxidation state comprising contacting the corresponding complex in an elevated oxidation state with lithium alkyl reducing agent and recovering the resulting product.

Description

. ~31-F 21 80558 PROCESS FOR PREPARATION OF REDUCED METALTlTANiUM COMPLEXES
The present invention relates to a process for preparing titanium or zirconium metal complexes in a reduced oxidation state. More particularly, the present process relates to 5 a process for preparing such metal complexes containing hyl, u~alL~ yf substituents in a high yield, facile manner. The resulting metal complexes are used for polymerizing rl-olefins includingethyleneaswellasvinylidenearomaticmonomers,suchasstyrene. Generallythe catalysts are activated for use by an activating cocatalyst such as an alkylaluminoxane or a cation forming compound. Such polymers may be usefully employed in the preparation of 10 solid objects and articles such as a moldings, films, sheets arld foamed objects by molding, casting or the like process.
In J. Am. Chem. Soc., 3, 581 ~1~61) the preparation of ~y~luL.~.ILa~ ylliLall;um dichloride bythe reaction of diisobutyl aluminum chloride with biscy~ fl titanium dichlorideisdisclosed. InGmelinHandbuchderAI)c.,u,a,,.,~l,r. Chemie,Springer-Verlag,p 5 134l(1977)~y~lo~ a~nyltitaniumdihalideswerestatedtobepreparedbyreductionofthe ~u~ l~,uo,-dil-g trihalide complexes using powdered zinc reducing agent in dry, oxygen free ~e~lal~J ' L ruran. Supported CpTiCI3 complexes were reduced by use of Et3AI, C3HsMgBr, and BuLi in React. Kinet. Catal. Lett., 16(2-3), 297-300 (1981). Finally, USP S,264,590 disclosed the reduction of ether complexes of Ti(lV) salts, exemplified bytitanium chlorides, using 20 organometallic or metal hydride reducing agents.
According to the present invention there is now provided a process for preparingtitanium or zirconium metal complexes corresponding to the formula:
CPmMXnXp wherein:
Cpisasingle~:~s-cy~lu~"~a~iel,;,lorrls-substitutedcyclopentadienylgroup~the substitutedcy,lop~ ad~ ,lgroupbeingoptionallyalsobondedtoMthroughasubstituentx as described hereinafter;
M is titanium or zirconium in the +3 oxidation state;
X each occurrence is an inert anionic ligand of up to 20 nonhydrogen atoms and 30 optionally one X and Cp are joined together forming the divalent ligand -CpX-;
X is an inert, neutral donor ligand;
misO,10r2;
n is an integer greater than or equal to 1;
p is independently 0 or 1; and thesumofmandnisequalto3, ~i~ENDcD ~EET ~-~
O _ _ _ . 4~31-F 2 ~ 80558 thestepsoftheprocesscomprisingcontactingametalcomplex.ur,e,,uond;l,~totheformula:
CpmM X~n+lxp wherein:
Cp, X', m, n and p are as previously defined:
M istitaniumorzirconium inthe ~40xidation state;

2s 3s ~,'END~D St~E~

~1 80558 X' each occurrence is an inert anionic ligand of up to ;!û nc."1,, ' uy~l, atoms with the provisothat in at leastone occurrence X' is ORwherein R is Cl-~O hydrocarbyl, and optionally one X~ and Cp are joined together forming the divalent -CpX'-;
with a lithium alkyl reducing agent and recovering the resulting product.
Al I reference to the Period ic Table Of the E I em ents herei n shal I refer tO the Periodic Table of the Elements, published and copyrighted by CRC Press, Inc,, l989. Also, any reference to a 6roup or Series shall be to the Group or Series as reflected in this Periodic Table of the Elements, utilizing the lUPACsystem for numbering groups.
As used herein, the term ~yl ,d;v~ refers to polymers having a stereoregular 10 structure Of greater than Sû percent syndiotactic Of a racemic triad as determined by ~3C nuclear magneticresonance~,ue~los~py~ Suchpolymersmaybeusefullyemployedinthepreparation of articlesandobjectsvia~omu,~,,;u,lmolding,injectionmoldingorothersuitabletechnique havinganextremelyhighresistancetod~rc,,,,,~JLi~Jllduetotheeffectsoftemperature Illustrative but nonlimiting examples of X include hydrocarbyl, silyl, halo, NR2 2,OR,SR,andBR2,whereinRisaspreviouslydefined. PreferablywhereXandRare hydrocarbyl the same are r~-bonded groups.
Illustrative but nonlimiting examples Of X' include ROR, RSR, NR3, PR3, and C2-20 olefinsordiolefins,whereinRisaspreviouslydefined. Suchdonorligandsareabletoform shared electron bonds but not a formal cova~ent bond with the metal.
Monocyclou~ d;cll;landsubstitutednlùnucy~l(Ju-~lladi~llylgroupsforuse accordingtothepresentinventionaremorespecificallydepictedbytheformula:
R' R"
R ~R ' R' wherei n:
R each occurrence is ;~d~ cd~. ,Lly hydrogen, halogen, R, N-RI, P-R2, OR; SR or BR2,whereinRisaspreviouslydefined,oroneortwopairsofadjacentR hyorocarbylgroups are joined together forming a fused ring system.
R individually may be R' or a divalent X group lor X~ group depending on whetherthereactantorproductcomplexisbeingreferredto~thatisalsocovalentlybondedtoM.
Preferably, R is alkyl or haloalkyl of up to 6 carbons. Most highly preferab~y Cp is ~y~lc,~_"L~ lorp~"L~ .l,Jlcyclopentadienyl.
Illustrative, but not limiting examples of metal complexes which may be used in the oreparation of the compounds of thls invention are derivatives of titanium or zircon~um.

SUBSTITUTE SHEET (hULE 26) Titanium is the preferred meta~. In a highly preterred process the complex is formed by reactionofcyc~ ad~ ltitaniumc14trialkoxidesorpentamethyltitaniumc~4 ~,i " ' withthereducingagent. Inamosthighlypreferredt,,.l,odi.,.c..~oftheinvention, Cpinthefinalproductisrls-cyclo~ ad;~ orrls-p~ oll~ lcyclopentadienyllmisone~M
5 is titanium, n is two, p is zero, X each occurrence is OR, and R is C1~ alkyl.Suitable lithium alkyl reducing agents especially include C~ 4 alkyl lithium compounds with n-butyl lithium, sec-butyl lithium and t-butyl lithium being preferred. A most highly preferred lithium alkyl reducing agent ist-butyl lithium. The amount of lithium alkyl compound used preferably varies from 0.9 to 2.0 moles per mole of starting complex, and most 10 preferably is from 1.0 to ~.S moles per mole of starting complex.
Recoveryoftheresultingcomplexisa~ lisl,~daccordingtoanyknown technique, usually bydevolatilization, extraction or precipitation upon addition of a poor solvent. Preferably a quenching agent such as a Cl 4 trialkylchlorosilane, especially i".~i,,l~l,lorosilaneisaddedtothereactionmixturetoreactwithunreactedlithiumalkylreducing agent or lithium alkoxide by-products. The amount of quenching agent used preferably varies from 0.9 to 2.0 moles per mole of starting complex, and most preferably is from 1.0 to l .S moles per mole of starting complex. The species formed upon addition of the quenching agent are generally volatile and may be removed from the solution by heating. The desired metal complexes are then removed by extraction in a h~ ' ~ ri~al l-c", solvent such as 20 hexane or a mixture of alkanes The complexes can be prepared in a suitable solvent at a temperature within the range from about -1 00C to about 300C. The reactants and products are generally sensitive to bothmoistureandoxygenandshouldbehandledandtransferredinaninertatmospheresuch as nitrogen, argon or helium. Suitable solvents or diluents for the complex preparation include 25 any of the solvents known in the prior art for metal complex formation including straight and branched-chainl,, ' ~..a,Lu,,,suchasC6.~2alkanes,especially,hexane.heptane,Oroctane;c6 ~2 cyclic and alicyclic hyd, c~al l--~ )s such as cyclohexane, cycloheptane, methylcyclohexane and methylc~,~lol .~"k,ne, C6 ,2 aromatic and alkyl-substituted aromatic compounds such as benzene~toluenelxyleneanddecalin;inertaliphaticethers~suchas~e~rall~ ' u~uran,dimethyl 30 ether and diethyl ether; and mixtures of the foregoing.
The resulting reduced metal complexes may exist in dimeric form or as coordinated adducts with neutral Lewis bases. The complexes are used in p~ . iLa~ioll reactions according to well known Ziegler-Natta reaction conditions. Typical p~,ly,~. iLa~ion conditions include slurry~ bulk or suspension p~ iLa~irJns using temperatures of from ooc t 35 160C. TypicalreactiontimesarefromoneminutetolOOhours,preferablyfromltolOhours.
An inert diluent or solvent may be used if desired. Examples of suitable diluents or solvents include C6-20 aliphatic, cycloaliphatic, aromatic and halogenated aliphatic or aromatic h,.' ~a,L,o.~j,aswell as mixturesthereof. Preferred diluentscomprisetheC6 ~oalkanes, tolueneandmixturesthereof. Aparticularlydesirablediluentforthepuly,l._.i,aIionisiso-ocune, iso-nonane or blends thereof such as Isopar-E~, available from Exxon Chemical Company. Suitable amounts of solvent are employed to provide a monomer v~ l IL,a~ion fromSpercentto100percentbyweight.
As in other similar p~,lr, . ,~ a Lions, it is highly desirable that the monomers and solvents employed be of sufficiently high purity that catalyst deactivation does not occur. Any suitable technique for monomer purification such as dev~ tili7~ on at reduced pressures, contactingwithmolecula~sievesorhighsurfacea~eaaluminaordeaerationmaybeemployed.
Having described the invention, the following examples are provided as further 1û illuStrativeandarenottobeconstruedaslimiting. Unlessstatedtothecontrary,allpartsand p_. ~el l~ay~i are based on weight.
Examole 1 Allreactionsandmanipulationswerecarriedoutunderinertatmosphereinadry box. Hexane solvent was purified by degassing, sparging with nitrogen and passing through 15 activatedaluminapriortouse.
A 100 mL Schlenk flask was charged with 1.05 9 (3.8 mmol~ of pentamethylcyclopentadienyl titanium ~ l,uA;d_ (Cp'Ti(OCH3~3) and 35 mL of t~al,~d.u~uran(THF). Theflaskwasplacedinadryi~ o~..upal~olslushbath(-78C). 2.4mL
of al.7MTHFsolutionoft-butyllithium~4mmol)wasaddedbysyringe. Theresultingsolution 20 was stirred for one hour Via a cannula, a solution of 0.5 cJ (4.6 mmol) of trimethylchlorosilane in 15 mL of THF was added dropwise with stirring. Over a 14 hour period, the resulting solution was allowed to slowly warm to room temperature with stirring. The volatiles were removed under reduced pressure. The resulting solid was extracted with hexane, the solution was filteredandtheproductrecrystalli-edat-1ooc Theproductwasaredcrystallinesolid, 25 identified by 1 H NMR and x-ray crystal structure analysis as the dimeric form of p~.l Lll;lcy-~lvpellla~ Jltitanium(111)d;~ llvA;d~.
POi ~ i La ~i ùl ~
A catalyst solution was prepared in a volumetric flask using toluene solvent. The requiredamountofpentamethylcy~lop~Lad;~ al~iul~l(lll)dirrl~lluA;d~(cp~Ti(ocH3)2) 30 wasweighedandaddedtothefla5kandtolueneaddedtoformaû.01 molarsolution.
Puly, iLa~iol~s were carried out in a septum capped, crimp sealed ampoule. rhe ampoule was charged with 10 ml of styrene and 75 yl of a 1 M solution polymethylaluminoxane (PMA)cocatalystintoluene. Thecatalystsolution(37~11)wasaddedandtheampoulewasthensealed and erl~ "' aLed at 70C in a water bath. The POIJ . .1~. iLa~iUl~ was quenched by the 35 additionofmethanolaheronehou~u~ly,l,~,;,a~iontime. Thepolymersamplewasisolated and the solvent evaporated. Percent conversion was 63 perceht. The polymer had a melting point in excess of 260C consistent with a sy~diu~a~ y of greater than 50 percent based on a racemic triad.

Claims (6)

WHAT IS CLAIMED IS:

1. A process for preparing titanium or zirconium metal complexes corresponding to the formula:
CpmMXnX'p wherein:
Cp is a single ?5-cyclopentadienyl or?5-substituted cyclopendienyl group, the substituted cyclopentadienyl group being optionally also bonded to M through a substituent x;
M is titanium or zirconium in the + 3 oxidation state;
X each occurrence is an inert anionic ligand of up to 20 nonhydrogen atoms and optionally one X and Cp are joined together forming the divalent ligand-CpX-;
X is an inert, neutral donor ligand;
m is 0,1 or 2;
n is an integer greater than or equal to 1;
p is independently 0 or 1; and the sum of m and n is equal to 3, the steps of the process comprising contacting a metal complex corresponding to the formula:
CpmM'X"n+1X'p wherein:
Cp, X', m, n and p are as previously defined;
M' is titanium or zirconium in the +4 oxidation state;
X" each occurrence is an inert anionic ligand of up to 20 nonhydrogen atoms withthe proviso that in at least one occurrence X" is OR wherein R is C1-10 hydrocarbyl, and optionally one X" and Cp are joined together forming the divalent ligand -CpX"-;
with a lithium alkyl reducing agent and recovering the resulting product.

2. The process according to claim 1 wherein M is titanium.

3. The process according to claim 1 wherein Cp is cyclpentadienyl or pentamethylcyclopentadienyl.

4. The process according to claim 1 wherein the complex is recovered by quenching with a C1-4 trialkylchlorosilane, devolatilizing the resulting solution and extracting the desired complex.

5. The process according to claim 3 wherein the C1-4 trialkylchlorosilane is trimethylchlorosilane.

6. The process according to claim 1 wherein the a alkyllithium reducing agent istert-butyl lithium.